Hans Lewandowski

Innovative methods in soil phosphorus research: A review

Phosphorus (P) is an indispensable element for all life on Earth and, during the past decade, concerns about the future of its global supply have stimulated much research on soil P and method development. This review provides an overview of advanced state-of-the-art methods currently used in soil P research. These involve bulk and spatially resolved spectroscopic and spectrometric P speciation methods (1 and 2D NMR, IR, Raman, Q-TOF MS/MS, high resolution-MS, NanoSIMS, XRF, XPS, (µ)XAS) as well as methods for assessing soil P reactions (sorption isotherms, quantum-chemical modeling, microbial biomass P, enzymes activity, DGT, 33P isotopic exchange, 18O isotope ratios). Required experimental set-ups and the potentials and limitations of individual methods present a guide for the selection of most suitable methods or combinations.

Interactions of 15 N-Sulfadiazine and Soil Components As Evidenced by 15 N-CPMAS NMR

The extensive use of sulfonamides (SNs) in animal husbandry has led to an unintentional widespread occurrence in several environmental compartments. The implementation of regulations and management recommendations to reduce the potential risk of development of antibiotic resistances necessitates detailed knowledge on their fate in soil. We present results from two independent incubation studies of 15N-labeled sulfadiazines (SDZ) which focused on identifying binding types in bound residues. In the first study 15N-amino labeled SDZ was incubated with two previously isolated humic acids in the presence and absence of Trametes versicolor laccase, while in the second study 15N-double-labeled SDZ was incubated with a typical agricultural Luvisol and the humic acid fraction isolated after sequential extraction of the soil. The freeze-dried humic acid fractions of both studies were then analyzed by 15N-CPMAS NMR and compared with the 15N-spectra of synthesized model compounds. In both studies amide bonds and Michael adducts were identified, while formation of imine bonds could be excluded. In the humic acid study, where less harsh extraction methods were applied, possible formation of H-bridging and sequestration were additionally detected.